Applications of mass spectrometry for the determination of the microbial crude protein synthesis in ruminants

The importance of quantifying ruminal microbial crude protein synthesis has promoted the development and comparison of several different methods for precise determination of both the amount and rate of synthesis. One major challenge is in estimating and differentiating protein in the rumen between microbial, dietary, and endogenous fractions, and to correctly isolate the solid and liquid microbial fraction of the rumen contents. This is further complicated by the goal of using non-invasive methods as much as is feasible, such as avoiding the use of fistulated animals; the selection of an appropriate microbial marker, specifically one that behaves similarly in the solid-associated and liquid-associated microbial fractions. It is also vital to be able to accurately estimate the contribution of microbial protein to overall nitrogen used by the animal, which can be accomplished by the use of 15N labeled, as assimilated by ruminal bacteria, and by the quantification of labeled nitrogen via mass spectrometry (15N/14N). This review focuses on challenges regarding accurate quantification of microbial crude protein synthesis in the rumen, as well as providing the methodology for quantification using the 15N marker. This review is based on the collection of scientific papers from the main research groups in feed and animal nutrition in ruminants

First Steps into Ruminal Microbiota Robustness

Despite its central role in ruminant nutrition, little is known about ruminal microbiota robustness, which is understood as the ability of the microbiota to cope with disturbances. The aim of the present review is to offer a comprehensive description of microbial robustness, as well as its potential drivers, with special focus on ruminal microbiota. First, we provide a briefing on the current knowledge about ruminal microbiota. Second, we define the concept of disturbance (any discrete event that disrupts the structure of a community and changes either the resource availability or the physical environment). Third, we discuss community resistance (the ability to remain unchanged in the face of a disturbance), resilience (the ability to return to the initial structure following a disturbance) and functional redundancy (the ability to maintain or recover initial function despite compositional changes), all of which are considered to be key properties of robust microbial communities. Then, we provide an overview of the currently available methodologies to assess community robustness, as well as its drivers (microbial diversity and network complexity) and its potential modulation through diet. Finally, we propose future lines of research on ruminal microbiota robustness

Renal and salivary excretions of plasma purine derivatives in swamp buffaloes and zebu cattle

This study compared the recovery rate of intrajugular-administered allantoin in the urine and saliva between swamp buffaloes and zebu cattle to examine whether it could explain the lower excretion rate of urinary purine derivatives (PD) in the buffaloes. Three male swamp buffalo yearlings, with an average body weight of 349±40.35 kg, and three Thai native cattle (154±3.26 kg) of similar age and sex were used in the study. Animals were kept in individual pens and fed at a maintenance energy level with a diet containing 65% monk bean husk (Vigna radiata) as roughage and 35% concentrates. Allantoin solution was infused into the jugular vein in four incremental rates equivalent to 0, 5, 10 and 15 mmol/d and urine was collected daily in acidified form. Daily PD excretion was linearly correlated with intrajugular allantoin infusion in both species. The relationship between daily urinary PD excretion (Y, mmol/d) and intrajugular allantoin infused (X, mmol/d) was Y = 0.75±0.318X+22.45±2.98 (r2 = 0.36, n = 12, MSE = 38.02, CV = 21.9, p<0.01) for swamp buffaloes and Y = 0.96±0.10X+15. 93±0.92 (r2 = 0.91, n = 12, MSE = 3.60, CV = 8.27, p<0.01) for zebu cattle. The salivary PD concentration was not correlated with intrajugular allantoin infusion in both species, with values for buffaloes numerically lower than those for cattle. The present study reconfirmed previous studies that buffaloes have a lower plasma PD excretion rate via the renal route and a significant proportion (22%) of the plasma PD loss is via the saliva. However, results of our present and previous studies suggest that differences in purine base (PB) metabolism between buffaloes and zebu cattle occur before the purine compounds reach the plasma pool